My Core + Bootloader Version for ATTiny's

Just for those who are interested, I have finally got around to uploading my version of the 'tiny' core for Arduino. Along with that I have included my version of Optiboot which works with the ATtiny84 and ATtiny85 processors (The optiboot version includes TinyTuner built in to calibrate the oscillator allowing a Software UART to be reliable).

The Core is hosted on github @:

Beta testers are very welcome as there are probably a few bugs in it which need ironing out (with the exception of the bootloader which is fully tested and functional).

I have also uploaded the fix for the PCREL error to the repository so it is easy to find.

I am still learning about my ATTiny 84 so this question may be simple, what is the advantage of the bootloader? Does it make it possible to use serial? If so, what pins would you use?

Currently, this my only resource that I have using.

Basically at the expense of 576B of flash you get to upload via serial port in the same way an arduino does. This means fewer pin need to be broken out for programming.
Another advantage is that my bootloader version tunes the internal oscillator which makes serial comma more reliable.